<!DOCTYPE html>
<html lang="en">
<head>
  <meta charset="UTF-8">
  <meta http-equiv="X-UA-Compatible" content="IE=edge">
  <meta name="viewport" content="width=device-width, initial-scale=1.0">
  <title>Document</title>

  <style>
    .img{
      width: 500px;
    }
    .img:hover{
      transform: scale(1.2);
      transition: all 0.3s;
    }
    .box{
      width: 500px;
      height: 500px;
      float: left;
      overflow: hidden;
    }
  </style>
  
</head>
<body>
  <div class="app">
    <div class="box">
      <img class="img" src="../img/1.png" alt="">
    </div>
    <div class="box">
      <img class="img" src="../img/2.jpg" alt="">
    </div>
    <div class="box">
      <img class="img" src="../img/3.jpg" alt="">
    </div>
  </div>
  
</body>
</html>